Surge system



K. c. BOTTENBERG ET AL 2,998,016

Aug. 29, 1961 SURGE SYSTEM 5 Sheets-Sheet 1 Filed June 1, 1959 Aug- 29,1961 K. c. BOTTENBERG ET AL 2,998,016

SURGE SYSTEM Filed June l, 1959 5 Sheets-Sheet 5 227 u; 524 gf 5 204i:205b 20Gb l 225" A T TOR/v5 ys 2,998,016 SURGE SYSTEM Kenneth C.Battenberg and Hurshel V. Hendrix, Bartlesville, Okla., and De WayneMaddox, Phillips, Tex.,

assignors to Phillips Petroleum Company, a corporation of Delaware Filed`Iune 1, 1959, Ser. No. 817,107 9 Claims. (Cl. 137-8) This inventionrelates to a surge system. In another aspect, it relates to a method andapparatus for supplying a normally liquid, volatile hydrocarbon feed tofractionators, or the like, at a constant rate from a source thereofhaving a normally variable rate of flow. In another aspect, it relatesto a method and apparatus wherein cooperative surface and subsurface, orunderground, surge facilities are used for supplying a normally liquid,volatile hydrocarbon feed, such as natural gasoline, to fractionators,or the like, at a constant rate from a source thereof having a normallyvariable rate of flow, such as a common header to which are connectedthe supply lines from a number of natural gasoline plants havingfluctuating outputs and variable capacities.

In various industrial processes or operations it is often necessary -tohave at all times an ample and constant supply of one or more materialsor feeds. For example, in the refining of natural gasoline it isnecessary that the supply of this product or feed to fractionatingtowers be relatively constant since such towers are designed andconstructed for a specific feed rate or range of feed rates. Where theavailable supply of such product is not constant or where it fluctuates,it is necessary to employ some type of surge system in order to supplythe product as feed having the requisite constant flow rate demanded bythe process or operation. -For example, in the refining of naturalgasoline the outputs of several plants are conveyed in a common streamto a surface surge tank of limited capacity, from which the product issupplied to fractionators at a constant rate of flow. Due to thedifferent capacities and periods of operation of the several plants, thecommon stream of natural gasoline will normally have a fluctuating orvariable flow rate different from that of the desired flow rate of thefeed sent to the fractionators for further processing.

Where the amount of supply or product conveyed to the surface surgesystem is variable and relatively large, the capacity of the surgesystem must of necessity be correspondingly large enough to accommodatethe product. Generally, this means that expensive steel tanks of massiveconstruction and capacity may be required. Such surge tanks must bedesigned to withstand the vapor pressure of the product. Moreover, wherethe product contains any substantial amount of solid, suspendedimpurities or foreign substances, such as iron sulfide, it is desirablethat such tanks have suficient volume to enable the settling of thesuspended impurities. If the product to be handled is normally avolatile liquid, such as natural gasoline or other hydrocarbons, thefilling and emptying of the surge tanks will also result in severebreathing losses due to changes in temperature during the heat of theday and the cool of the night. While these losses can be reduced byproviding the storage tanks with breather roofs or the like, suchequipment is relatively costly and does not eliminate all of the lossesof valuable product, or completely insure the safe handling of theVolatile hydrocarbon.

The problem of adequate storage in surge facilities is also aggravatedwhere the product handled is one which experiences seasonal peak demandand corresponding seasonal slack periods, such as that common to thenatural gasoline and liquefied petroleum gas industries. Thesefluctuations in demand also require large storage Patented Aug.v 29,1961 ICC facilities. The use of large, high pressure, sealed tanks forthis purpose necessarily entails greater expense in the handling andstorage of the product. In many cases the large bulk storage of productis not economically feasible.

Accordingly, an object of this invention, is to provide an improvedsurge system. Another object is to provide lan improved method and.apparatus for supplying a normally liquid, volatile hydrocarbon feed tofractionators, `or the like, at a constant rate from a source thereofhaving a normally variable rate of flow. Another object is to provide amethod and apparatus wherein cooperative surface and subsurface, orunderground, surge and storage facilities are used for supplying anormally liquid, volatile hydrocarbon feed, such as natural gasoline, tofractionators or the like, at a constant rate of flow from a variablesource thereof, such as a common header to which are connected thesupply lines from a number of plants having fluctuating outputs andVariable capacities. Another object is to provide a surge system oflarge capacity which is relatively unaffected by changes in ambienttemperature. Another object is to provide a surge system havingsufiiciently large capacity to enable the effective settling of solidimpurities and permit the composition of product handled to stabilize.Another object is to minimize the breathing losses during the handlingof relatively high volatile, normally liquid hydrocarbons. A furtherobject is to provide a safe, reliable, and relatively economicalimproved surge system for handling normally liquid, volatilehydrocarbons, such as natural gasoline. Further objects and advantagesof this invention will become apparent to those skilled in the art fromthe following discussion, appended claims, and accompanying drawing inwhich:

FIGURE l is a diagrammatic view in elevation and partial section of oneembodiment of the surge system 0f this invention;

FIGURE 2 is a view similar to FIGURE l illustrating another embodimentof this invention; and

FIGURES 3 and 4 are diagrammatic views of control systems which can beused in automatically controlling the surge systems of FIGURES l and 2,respectively.

The normally liquid, volatile hydrocarbons used in this inventionincludes any of those which are normally liquid under the conditions ofoperation of this invention, such as natural gasoline, straight run orcracked gasoline, kerosene, liquefied petroleum gas, crude oil, and thelike.

Reference will now be made to the accompanying drawing wherein likeparts have been designated with like reference numbers. For purposes ofillustration and description, the subject invention will be hereinafterset forth by showing its utility in the handling of natural gasoline,although it -is to be understood that it is not to be limited theretosince it is applicable wherever it is desired to handle any highlyVolatile, normally liquid hydrocarbon or the like.

Referring to FIGURE l, one or more streams of natural gasoline areconveyed or pumped via lines 6 and 7 to a common point or header, lineS, the ow rate in this header normally fluctuating or varying, e.g.,from hour to hour, night and day, week to week, season to season, etc.Further, the compositions of the various streams may differ, eg.,sometimes the natural gasoline may be almost pure propane. The supply ofnatural gasoline in line 8 is conveyed to a surface surge tank 9, suchas a cylindrical steel tank of limited capacity, the liquid level inthis tank being constantly monitored by means of a suitable liquid levelcontroller 10. From the surge tank 9, natural gasoline is withdrawn asrequired via line `11 and pumped by means of pump 12 to feed line 13.The feed rate in line 13 is maintained at a relatively constant Value(i.e., at fixed rate, or within a range of feed rates) by means of aflow controller 14 and a suitable flow control valve 16 which isoperatively connected to flow controller 14, the natural gasoline feedin line '13 being conveyed to fractionators or the lik e for furtherprocessing. When the rate offlow of natural gasoline in lines 6, 7 isgreater than that desired Yfor constant rate of flow in line 13, some ofthe natural gasoline from lines 6, 7 is conveyed by line 17, having apump 18 therein to an underground storage cavern generally designated19, the portion of line 17 downstream from pump 18 having a check valve21 therein.

Underground cavern 19 is formed in a generally impermeable earthformation, either by conventional mining methods, or, preferably, bydissolving out a soluble material with solvents to creat a storage spacein the soluble formation, for example a salt dome.

Since the cavern is located below ground, the contents thereof are notsubjected to the fluctuating ambient temperatures above ground, thetemperature underground being relatively constant. Such storage space isfar more economical than V4would be surface storage or surge tanks aboveground having comparable capacity. The underground cavern comprises acavity 22 formed within a soluble* formation 23, such as salt, with anoverlying formation 24 thereabove. The underground cavern 19 is providedan access bore 26 which communicates with the cavity 22. DependingWithin the access bore 26 is a casing 27 which is cemented in place withcement 28 to provide the cavern Witha huid-tight seal. Depending Withincasing 27 is a string of tubing 29, an annulus 30 being formed betweenthe string 29 and casing Z7, the lower end of the string 29 dependingbeneath the lower end of casing 27. If desired, another string of tubing31 can be inserted within the string 29, an annulus 32 being formedtherebetween, the lower end of the inner string 31 depending below thelower end of the outer string 29. A pool of displacing liquid 33, suchas brine, occupies the lower portion of the cavern with a layer 34 ofthe immiscible, lighter stored product, natural gasoline, thereaboveoccupying the upper portion of the cavern, an interface 3S being formedbetween the product 34 and brine 33.

Because of the large, economical storage space provided by theunderground cavern, the stored product therein will have suiicientresidence time to enable the composition thereof to become stabilized.Further, this large storage space permits foreign materials, such asiron sulfide, normally suspended in the introduced product, to drop outand settle in the bottom of the cavern.

The product 34 within the cavity 22 can be supplied to surge tank 9 vialine 36 and supply line 8, line 36 corurnunicating at the surface withthe annulus 30 and having a suitable flow control valve 37 therein. Inorder to effect the withdrawal of product 34 from cavity 22, displacingliquid can be pumped via lines 39 and 38 from brine supply 41, such-as abrine tank or pit, the displacing liquid being injected tinto the upperend of the inner string of tubing 31. Line 39 is provided with asuitable pump 42 and a check valve 40. To insure control over thedisplacing liquid, line 39 can beV provided with a by-pass line 43,by-passing pump 42, the by-pass linef having a siutable ilow controlvalve 44 therein operatively controlled by pressure controller 45 whichis operatively connected to line 43. During the lling of cavity 22 withproduct 34, the brine 33 is displaced from the underground cavern 19 viainner string of tubing 31 and conveyed via line 38 to the brine supplytank 41, line 38 having a suitable flow control valve 46 therein.

As mentioned hereinbefore, the liquid level within surge tank 9 isconstantly monitored by liquid level controller 10. .t The latterinstrument is operatively connected to pumps 18 and 42, controlling theoperation thereof, and is also operatively connected to dow control p Y2, the various streams 6 and 7 of natural gasoline are conveyed by acommon header 51 to an underground cavern generally designated 52. Thiscavern is in some respects similar to that of FIGURE l. Cavern 52comprises a cavity 53 formedwithin a soluble formation 23, such as salt,above which formation there is an overlyingformation 24. The cavern 52is provided with access bore 54 in which is cemented a casing 56.Depending within casing S6 is a string of tubing 58, an annulus 59 beingformed therebetween, the lower end of the inner string,pdepending belowthat of the casing. The annular space 59 is connected at the surface toa l-ine 61 which in turn is connected to a line 62 for supplying thestored product 63 from the cavern 52 to a surface surge tank 9. Thelatter surge tank is also provided with a liquid level controller 63which constantly monitors the level of a natural gasoline within thesurge tank. Withdrawal of the natural gasoline from surge tank 9 can beeffected in a manner like that of FIGURE l. It is thus seen that in theembodiment of FIGURE 2 all of the natural gasoline supply is conveyed tothe underground cavern 52 before it is conveyed to the rsurge tank 9.

Where the rate of llow of a natural gasoline within line 61 is greaterthan that desired in the feed line 13, the product 63 withdrawn from thestorage cavern 52 it is also pumped by pump 65 and conveyed via line 66to underground cavern 67, the line 66 havingV a check valve 68 therein.

The underground cavern 67 is similar to underground cavern 52, cavern 67being provided with a casing 69 and `inner string of tubing 71 with anannulus 72 formed therebetween. Line 66 communicates via line 73 withline 62 when it is desired to withdraw the natural gasoline 74 Vfromcavern 67, line 73 being provided with a flow control valve'76. Thelower portion of cavity 77 is occupied by a pool of brine 78, thefilling and emptying of the displacingrliquid being effected by means ofline 79 connected at one end to the upper end of string 71 and at theother end toa gravity -ow brine tank or pit 81. The underground cavern52 can be similarly provided with a gravity flow brine tank, but has notbeen shown in the drawing for purposes of brevity.

The liquid level controller 63 is operatively connected to pump 65 andflow control valve 76, controlling the operations thereof.

In the operation of the surge system set forth in FIG- URE l, naturalgasoline is conveyed through lines 6 and 7 at a normally variablerilowrate. Some or all of the natural gasoline passes to the surface surgetank `9 and from the latter it is conveyed via line 13 to fractionatorsor other processing equipment at a constant flow rate. The liquid levelof natural gasoline within surge tank 9 is constantly monitored by meansof liquid level controller 10. The liquid level in surge tank 9 willrise and fall between a predetermined high level a and a predeterminedlowV level b. When theY liquid level controller 10 senses a rise inliquid level within tank 9 to the predetermined high level a, indicatinga large supply of natural gasoline lin that tank, the liquid levelVcontroller operatively causes the operation of pump 118, permitting partof the supply of natural gasoline to be pumped and conveyed via line. 17to the underground cavern 19 and at the same time a part of the supplyis conveyed via line Sto the surge tank 9. The liquid level controller10 also is operatively adapted to prevent the Withdrawal of the product34 from the-V cavern 19 Vby maintaining the ow control valve 37 in aclosed position. At the same time, with pump 1S in operation, the liquidlevel control- -ler maintains the flow control valve 46 in line 38 in anopen position so as to permit the brine 33 in the cavern 19 to bedisplaced to brine tank 41 via line 38.

When the liquid level in surge tank 9 falls to a point intermediate.,and half-way between predetermined levels a and b, liquid levelcontroller stops pump 18 and closes valve 46.

When liquid level controller 10 senses the drop in the level of thenatural gasoline in tank 9 to the predetermined low value b, indicatinga low supply of gasoline in tank 9, the liquid level controlleraccordingly operatively starts pump 42, causing the brine in the brinetank 41 to be pumped via lines 39 and 38 into the tubing string 31, thebrine introduced into the cavity 22 of the cavern 19 causing thedisplacement of the stored natural gasoline 34. At the same time, theliquid level controller 10 operatively opens the ow control valve 37 inline 36, allowing the displaced natural gasoline to be conveyed via line36 to the supply line `8.

When the liquid level in surge tank 9 rises to a point intermediate andhalf-way between predetermined levels a and b, the liquid levelcontroller 10 stops pump 42 and closes valve "37.

If the liquid level in surge tank 9 rises to predetermined high level a,or falls to predetermined level b, the sequence of operations asdescribed above is repeated to bring the level to the intermediate pointbetween levels a and b.

As an example of a liquid level control system which can be used incarrying out the operation of the embodiment shown in FIGURE 1,reference will now be made to the control system diagrammaticallyillustrated in FIGURE 3.

In FIGURE 3, a iloat 101 is adapted to float on the top of the naturalgasoline in the surge tank 9 of FIGURE l. The oat 101 is connected to amovable arm 102 which is pivoted at 103. The arm 102 has associatedtherewith four pairs of electrical contact: 104@ and 10'4b, 105:1 and105b, 106a and 106b, and 107a and 107b. These pairs of contacts areadapted to come into juncture and break with the rise and fall of thefloat 101, thereby making and breaking electrical circuits, energizingand de-energizing solenoid coils, opening and closing switches -inelectrical circuits, and thereby alternately starting and stopping themotors of the pumps 18 and 42 and opening and closing the valves 37 and46 illustrated in FIGURE l.

The upward movement of arm 102 is biased by a spring or ilexible wireattached to contact 106b, and the arms `downward movement lbiased by asimilar flexible wire attached to contact 104a, contacts 106b and 10451being attached to the arm 102. Contacts 105a `and b, and 107a and bhaving springs attached thereto which limit the maximum distances theycan extend to the positions shown in FIGURE 3, lat which position theyare in juncture.

When oat 101 rises to the predetermined high liquid level a, junction ismade between contacts 106a and 106b, thereby completing an electricalcircuit 108 which causes the energizing of a solenoid coil 109. When thelatter is energized, link 110 is pulled downwardly in opposition to aspring 111 tending to retain the link 110 in the position shown. As link110 moves downward, a pivoted lock arm 112 slides along the inclinedsurface of the link, this pivoted lock arm 112 being pulled to the rightby a spring 113. When the link 110 has moved downwardly a sufficientdistance, the lock arm 112 occupies a locking position adjacent theupper at face of the link 110, locking the link 110 in its downwardposition. When the link 110 is in its downward position, it causesswitch 114 to close, thereby completing the electric circuit 116,causing t'ne operation of pump 18. The downward movement of the link 110also causes switch 117 to close, thereby completing electric circuit11S, causing solenoid coil 119 to energize. When the latter isenergized, pivoted arm 121 moves downward in opposition to spring 122,thereby causing instrument air line 123 to increase the air pressure inair line 124 connected to valve 46 in line 38, causing the valve 46 toopen.

As the surge tank 9 drops in level, the junction between contacts 106aand 106b is broken, but pump 18 continues to operate and valve 46 ismaintained in an open position because the pivoted locking arm 112prevents link 110 from moving to its upper position, despite thede-energizing of solenoid coil 109. However, when the liquid level inthe surge tank 9 reaches an intermediate liquid level betweenpredetermined liquid levels a and b, the float actuated arm 102 occupiesthe horizontal position shown in FIGURE 3. In this position, junction ismade between contacts 107a and 1Mb, completing the electric circuit 126and thereby energizing solenoid coil 127. When the latter is energized,lock arm 112 is pulled to the left, in opposition to spring 113, therebyunlocking the link 110 and allowing its movement to its upper position.As a result, switches 114 and 117 are broken and pump 18 is stopped andvalve 46 is closed.

When the liquid level in surge tank 9 falls to the predetermined lowliquid level b, the lioat 101 moves accordingly and causes contacts 104uand 104b to come to junction, thereby completing electric circuit 128and causing solenoid coil 129 to energize. When the latter is energized,link 131 is pulled downward, the pivoted locking arm 142 sliding alongthe inclined surface of the link, the pivoted arm 142 being pulled tothe right by spring 143 to a locking position. When the link 131 -is inits downward position, switch 132 is closed, thereby completing theelectric circuit 133 and causing pump 42 to operate. The downwardmovement of the link 131 also causes switch 134 to close, therebycompleting the electric circuit 135 which causes solenoid coil 136 toenergize. When the latter is energized, pivoted arm 137 moves'downwardly in opposition to spring 138, thereby causing the air ininstrument air line 139 to increase the air pressure in air line 141,causing valve 37 in line 36 to open. When the liquid level in the surgetank 9 begins to rise, the junction between contacts 104a and 10411 isbroken, but pump 42 continues to operate and valve 37 is maintained inan open position because the link 131 is locked by pivoted arm 142 inits downward position, despite the de-energizing of the solenoid coil129.

When the liquid level in surge tank 9 reaches its intermediate positionbetween predetermined levels a and b, junction is made between contacts105a and 105b, thereby completing the electric circuit 144, causingsolenoid coil 146 to energize. When the latter is energized, locking arm4142 is pulled to the left, in opposition to spring 143, therebyunlocking the link 131, allowing it to move to its upper position andopen switches 132, 134, causing pump 142 to stop and valve 37 to close.

In the operation of the embodiment set forth in FIG- URE 2, all of thesupply of natural gasoline from the processing plants or source ofsupply is conveyed via line 51 to the underground cavern 52. Because ofthe large capacity o ,f cavity 53, suspended foreign material, such asiron sulfide, drops out of the product introduced into the cavern 52 andsettles in the bottom thereof Where its presence is harmless in that itneed not be removed or otherwise be of concern. From cavern 52, thenatural gasoline is then conveyed via lines 61 and 62 to the surge tank9. The liquid level controller 63 constantly monitors the height of theliquid level within the surge tank 9, the level rising and fallingbetween predetermined levels a and b. vIf the level within surge tank 9rises to predetermined high value a, it operatively causes pump 65 tostart up, while valve 76 in line 73 is in a normally closed position.When the liquid level falls to a point intermediate and half-way betweenpredetermined levels a and b, liquid level controller 10 stops pump 65.

When the liquid level controller 63 senses a drop in the level withinsurge tank 9 to predetermined value b, the liquid level controller 63operatively opens valve 76, permitting brine in tank 81 to flow underthe force oli gravity intoi the cavern 67 and causethe natural gasoline74 to be displaced from that cavern 67 via annular space 72, thedisplaced natural gasoline then flowing Yfrom cavern 67 .via lines 66and 73 to the supply line' 62. When the liquid level rises to a pointintermediate and half-way between predetermined levels aand b, liquidlevel controller 63 closes valve 76.

If the liquid level in surge tank 9 rises to predetermined high level a,or falls Vto predetermined level 6, the sequence of operations asdescribed above is repeated to bring the level to the intermediate pointbetween levels a and b.

As an lexample of al liquid level control system which can be used inthe operation of the embodiment shown in FIGURE 2, referencefwill now bemade to the control system diagrammatically shown in FIGURE 4, which insome aspects is similar to that of FIGURE 3.

In FIGURE 4, a oat 201 is adapted to oat on the top of the naturalgasoline in the surge tank 9 of FIG- URE 2. Float 201 is connected tofloat arm 202 which is pivoted at point 203. This float arm 202 hasassociated therewith four pairs of electrical contacts, 204g and 2046,205:1 and 205b, 206a and 20Gb, and 207a and 207b. With the rise and fallof Vthe float arm 202, these contacts come into junction and are broken,thereby making and breaking electrical circuit, energizing anddeenergizing certain solenoid coils, thereby opening and closing certainswitches to cause the starting and stop-` ping of pump 65 and theopening and closing of valve 76.

-In FIGURE 4, when the liquid level in surge tank 9 rises to thepredetermined high liquid level a, junction is made between contact 205eand 205b, thereby completing electric circuit 208, causing solenoid coil209 to energize.

When the latter is energized, link 210 is pulled to a downward position,the locking arm 212 sliding along the inclined surface of the link to alocking position, this arm 212 being pulled to the right by a spring213. When the link 210 is in its downward locked position, switch 214 isclosed, thereby completing electric circuit 215 which causes pump 65 tooperate. When the liquid level in the surge tank 9 begins to fall, thejunction between contacts 205a and 205!) is'broken, thereby causing coil209 to deenergize. However, the link 210 is held in its downward lockedposition by locking arm 212, so as to continue the operation of pump 65.When the level in the surge 9 reaches its intermediate position,contacts 207e and 2071 come into junction, thereby completing electriccircuit 216v causing solenoid coil 217 to energize. When the latter isenergized, the locking of 212 is pulled to the left, in'opposition tospring 213, thereby unlocking link 210 and allowing it -to return to itsupper position. As va result, switch 214 is broken and pump 65 stops.

When the liquid level within the surge tank 9 of FIG- URE 2 reaches itspredetermined low liquid levelV b', junction is made between contacts204a and 204b, thereby completing electric circuit 218 and causingsolenoid coil 219 to energize. VWhen the latter is energized, link 220is pulled in a downward position, the locking arm 222 sliding along theinclined surface of the link to a locking position, the movement of thelocking arm 222 along the inclined surface being aided by the pulling ofspring 223. In its downward locked position, the link 220 causes switch224 to close thereby completing electric circuit 225 and causingsolenoid coil 226 to energize` When the latter 'is energized, pivotedarm 227 is pulled downwardly, in opposition to spring 228, therebycausing the air in instrument air line 2-29 to increase the air pressurein air line 230, whereby valve 76 in line 73 is open.

When the liquid level in surge tank 9 begins to rise, the junctionbetween contacts 204a and 2041) is broken, but the valve 76 ismaintained in its open position because the link 220 is locked inposition by locking arm 222. However, when the liquid level in the surgetank 9 reaches a point intermediate its predetermined levels a and b,junction is made vbetween contacts 206a and 206B, there- Variousmodifications and alterations of this invention v will become apparentto those skilled in the art from the foregoing discussion andaccompanying drawing, and it should be understood that the instantinvention is not to be unduly limited to that set forth hereinbefore forillustrative purposes.

We claim:

l. A process for supplying a liquid at a constant ilow rate from asource thereof having a normally variable flow rate, which comprisespassing said liquid from said source to a surface surge zone,withdrawing said liquid from said surface surge zone and passing ittherefrom at said constant flow rate, continuously monitoring the liquidlevel of said liquid in said surface surge zone, passing a portion ofsaid liquid from said source to an underground surge zone when theliquid level in said surface surge zone reaches a predetermined highliquid level, and passing liquid from said underground surge zone tosaid surface surge zone when the liquid level in said latter zonereaches a predetermined low liquid level.

2. The process according to claim l wherein said underground surge zonecomprises a cavern formed within an underground impermeable formationhaving an access bore communicating with ground surface with a pool ofliquid displacing medium heavier than and immiscible with said liquidoccupying the lower portion of said cavern.

3. The process according to claim 2 wherein said liquid displaces saidliquid displacing medium from said cavern when said liquid is introducedtherein, and wherein said liquid is displaced from said cavern by saidliquid displacing medium when said liquid is passed to said surfacesurge zone.

4. A process for supplying a liquid at a constant flow rate from asource thereof having a normally variable llow rate, which comprisespassing said liquid from said source to aY surface surge zone,withdrawing said liquid from said surface surge zone and'passing ittherefrom at said constant ow rate, continuously monitoring the liquidlevel of Said liquid in said surface surge zone, said liquid levelnormally varying in height betweena predetermined high liquid level anda predetermined low liquid level, passing a portion of said liquid fromsaid source to an underground surgev cavern when the liquid level insaid surface surge Vzone reaches said predetermined high liquid level,said cavern comprising a cavity formed within an underground impermeableformation and having an access fbore communicating with the groundsurface, the lower portion of said cavity being normally occupied by apool of liquid displacing medium heavier than and immiscible with saidliquid, said liquid displacing said displacing medium from said cavernwhen said liquid is introduced therein, discontinuing the passing ofsaid liquid into said cavern when the liquid level in said surface surgezone falls to a point intermediate said predetermined liquid levels,passing said liquid from said cavern to said surface surge zone when theliquid level therein falls to said predetermined low liquid level, saiddisplacing liquid being introduced into said cavern to thus displacesaid liquid therefrom, and discontinuing the withdrawal of said liquidfrom said cavern when the liquid level in said surface surge zonereaches said point intermediate said predetermined liquid levels.

5. The process according to claim 4 wherein said liquid is naturalgasoline, and said displacing medium is brine.

6. A process for supplying Va liquid at a constant ow rate from a sourcethereof having a normally variable ow rate, which comprises passing saidliquid from said source to a first underground surge cavern,continuously withdrawing said liquid therefrom and passing it to asurface surge zone, withdrawing said liquid from said surface surge zoneand passing it therefrom at said constant flow rate, continuouslymonitoring the liquid level of said liquid in said surface surge zone,said liquid level normally varying in height between a predeterminedhigh liquid level and a predetermined low liquid level, passing aportion of said liquid from said cavern to a second underground surgecavern when the liquid level in said surface surge zone reaches saidpredetermined high liquid level, said second cavern having a pool ofliquid displacing medium normally occupying the lower portion thereofand heavier than and immiscible with said liquid, said liquid introducedinto said second cavern displacing said displacing medium therefrom,discontinuing the passing of said liquid to said second cavern when theliquid level in said surface surge zone falls to a point intermediatesaid predetermined liquid levels, passing said liquid from said secondcavern to said surface surge zone when the liquid level therein falls tosaid predetermined low liquid level, said displacing medium beingintroduced into said second cavern to thus displace said liquidtherefrom, and discontinuing the withdrawal of said liquid from saidsecond cavern when the liquid level in said surface surge zone reachessaid point intermediate said predetermined liquid levels.

7. A surge system comprising, in combination, a sur face surge tank, afeed supply line and a feed withdrawal line connected to said tank, owrate control means connected to said feed withdrawal line to maintainthe flow therethrough at a constant rate, liquid level control meansadapted to continuously monitor the liquid level in said tank, saidliquid level normally varying between a predetermined high liquid leveland a predetermined low liquid level, an underground surge cavern, thelatter comprising a cavity formed within an underground impermeableformation and having an access bore communicating with ground surface, apool of liquid displacing medium normally occupying the lower portion ofsaid cavity, a first line connected to said feed supply line and saidaccess bore, first pump means in said first line, a second lineconnected to said access bore and said tank, first oW control means insaid second line, a source of said displacing medium, a third lineconnected between said source and said pool of liquid displacing medium,second ow control means in said third line, -a fourth line connectedbetween said source and said pool of liquid displacing medium, andsecond pump means in said fourth line, said pump means and flow controlmeans operatively connected to said liquid level control means, saidfirst pump means being operated and said first flow control means beingclosed and said second flow control means being opened when said liquidlevel reaches said predetermined high liquid level, said second pumpmeans being operated and said first flow control means being opened andsaid second flow control means being closed when said liquid level fallsto said predetermined low liquid level.

8. A surge system comprising, in combination, a first undergound surgecavern, a feed supply line connected to said cavern, a surface surgetank, a first line connected between said cavern and said tank, a feedwithdrawal line connected to said tank, ow rate control means connectedto said feed withdrawal line to maintain the flow therethrough at aconstant rate, liquid level control means adapted to continuouslymonitor the liquid level in said tank, said liquid level normallyvarying between a predetermined high liquid level and a predeterminedlow liquid level, a second undergound surge cavern, a second lineconnected between said first and second caverns, pump means in saidsecond line, a third line connected between said second cavern and saidtank, and flow control means in said third line, a source of liquiddisplacing medium, a fourth line connected between said source and apool of liquid displacing medium normally occupying the lower portion ofsaid second cavern, said pump means and ilo-w control means beingoperatively connected to said liquid level control means, said pumpmeans adapted to operate and said flow control means adapted to clo-sewhen said liquid level reaches said predetermined high liquid level,said flow control means adapted to open when said liquid level falls tosaid predetermined low liquid level and permit gravity flow of saidliquid displacing medium from said source to said pool to displace saidliquid from said second cavern through said second and third lines tosaid surface surge tank.

9. The surge system according to claim 7 wherein said liquid displacingmedium is heavier than and immiscible with said liquid.

References Cited in the file of this patent UNITED STATES PATENTS2,085,526 Diescher June 29, 1937

